1. Field of Invention
The present invention relates to an anchor pre-tensioner for a safety seat belt of a vehicle, and more particularly, to an improved anchor pre-tensioner for a safety seat belt of a vehicle to prevent a webbing of a safety seat belt from being caught in the passenger's belly in collision.
2. Description of Related Art
In general, a vehicle has seat belts to prevent a driver and passengers from injuries due to external shock such as a collision. The seat belt protects a driver and passengers from collision energy of a vehicle alone, but has a major role of protecting the passengers safely with the assistance of an airbag system.
In order to ensure the safety of passengers who habitually wear a seat belt in an inappropriate way, for example, a loose seat belt, the seat belt is provided with an anchor pre-tensioner which is effective to remove webbing slack of the seat belt, in addition to a retractor pre-tensioner.
The anchor pre-tensioner of a seat belt is a device to apply a preset tension to the seat belt, when a vehicle collides, to remove webbing slack, to enhance the initial restraint ability of the seat belt such that a restraint system may effectively absorb collision energy.
A submarine phenomenon occurs on the seat belt in the collision of a vehicle. The submarine phenomenon generally refers to phenomenon that a dummy is moved down relatively from the seat belt. There are several problems during the submarine phenomenon; one of them is a phenomenon that a webbing of the seat belt moves relatively upward by the downward movement of the dummy and thus is caught in the belly, namely, a phenomenon of the webbing of a seat belt caught in the belly. This submarine phenomenon frequently occurs to a 5% ile dummy having the small pelvis and the low belly.
North American NCAP estimates a vehicle from 11MY (Year of Make) in the front collision under the conditions where a 5% ile female dummy is seated on the passenger seat, whereas Korea has a plan of performing the estimation from 2013 and Europe from 2015 to reinforce safety of a vehicle. Moreover, China conducts the estimation of a vehicle under the conditions where a 5% ile dummy is seated on the rear passenger seat in NCAP from 2012, while reflecting whether not only injury but the submarine phenomenon occur to the estimation.
The drawbacks of the submarine phenomenon, that is, the webbing of the seat belt caught in the belly occurs when, in the collision, the webbing of the seat belt moves upward and from the pelvis of the dummy to the belly excessively and presses the belly without muscles and bones, resulting in excessively pressing the belly. Seating of the webbing on the belly of weak rigidity brings the pelvis of the dummy to move farther so that laps of the dummy may be injured more seriously and that unstable mobility of the upper part of the dummy may bring an unexpected mobility of the dummy, and that the belly pressure may bring the rupture of the internal organs and the like in actual collision accident.
There are essential factors of the phenomenon that the webbing of the seat belt is caught in the belly such as acceleration of a vehicle itself, a pitch angle (a pitch angle when a large portion of the webbing is caught in the belly), an intersection of the anchor pre-tensioner of the seat belt and buckle height, and cushion stiffness of a seat.
Thus, the factors must be improved for the enhancement of the caught webbing of the seat belt in the belly, but there are several difficulties as follows:
Acceleration of a vehicle among the factors is measured by an acceleration sensor mounted in the vehicle at the collision and affected by overall properties of the vehicle such as the body structure, the chassis structure, engine size, etc. The caught webbing of the seat belt in the belly may be enhanced by changing the acceleration. However, it is actually difficult to enhance the caught webbing of the seat belt in the belly because the change needs serious modification in the vehicle structure.
The pitch angle of a vehicle refers to an angle of lift and rotation of the rear side of a vehicle in the collision and is affected by the overall properties such as the body structure, the chassis structure, the engine size, etc. of the vehicle. The improvement of the body structure may enhance the caught webbing of the seat belt in the belly partially but acceleration and deceleration of the vehicle body are inferior.
The APT intersection of the seat belt is determined as a relative position between a mounting position of the anchor pre-tensioner and the dummy. Since the anchor pre-tensioner is usually arranged by a B-pillar and must secure the mounting space, it is difficult to change the mounting position due to interference between parts when the mounting position is determined. It is difficult to change the mounting position of the dummy because the mounting position thereof is determined by an interior package.
It is relatively easy to change the buckle height of the seat belt but there is possibility of deterioration due to inconvenience in use of the buckle when the buckle height is reduced for the enhancement of the caught webbing of the seat belt in the belly.
Moreover, it is difficult to change the cushion stiffness of the seat and the increased cushion stiffness deteriorates the ride comfort.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.